#!/usr/bin/env python

import random

t = random.randint(1, 30)

print "%d" % (t)
for i in range(0, t):
    h = random.randint(0, 23)
    m = random.randint(0, 59)

    if i > t / 3:
        m = 0

    print "%02d:%02d" % (h, m)
